1. Field of the Invention
The present invention is related to a circuit capable of automatically calibrating a resonant frequency of an antenna and method thereof, and particularly to a circuit and method thereof that can utilize a capacitor array with an adjustable value to calibrate a resonant frequency of an antenna automatically.
2. Description of the Prior Art
In a radio frequency identification (RFID) system, a reader transmits a modulation signal by an antenna thereof, then a signal receiver utilizes an antenna with a resonant frequency the same as a resonant frequency of the antenna of the reader to receive the modulation signal, and demodulates the modulation signal. However, because an inductor and a capacitor of the signal receiver have errors, an error usually exists between the resonant frequency of the signal receiver and the resonant frequency of the reader, resulting in the radio frequency identification system having a shorter operation distance. Therefore, integrated circuit process variation increases difficulty for a designer of the signal receiver to design a signal receiver that operates well.